1. Field of the Invention
The present invention relates an automatic focusing camera provided with an IC for use in an automatic focusing process.
2. Background Arts
Most of commercially available cameras are provided with an automatic focusing mechanism, a motor-driven zooming mechanism, an automatic film winding mechanism, and electronic circuits for operating these mechanisms. Among various types of automatic focusing mechanisms, an infrared active type has been popularly used in economy price compact cameras. The infrared active type automatic focusing mechanism uses a light projecting-receiving section having an infrared light emission diode (IRED) that emits infrared rays through a projection lens toward a photographic subject, and a position sending device (PSD) that receives through a photoreceptive lens the infrared rays reflected from the subject. A detection signal from the PSD is fed to an IC specific to the automatic focusing mechanism, hereinafter called the autofocus IC, and the autofocus IC processes the detection signal to produce a subject distance signal. Based on the subject distance signal, a lens drive device of the automatic focusing mechanism brings a taking lens to a focusing position under the control of a CPU.
In such an electronic compact camera, electronic components of control circuits, including the autofocus IC, are mounted or formed on flexible printed circuit boards, and the flexible printed circuit boards are folded into a small size to mount them in a narrow space inside the camera. Also a switch for detecting when and how much degree a release button is pressed down, hereinafter called the release switch, is mounted on the flexible printed circuit board, and is placed underneath the release button.
On the other hand, since the autofocus IC processes the detection signal from the PSD of the light projecting-receiving section, the autofocus IC is often located above the light projecting-receiving section that is usually mounted in an upper front portion of the camera. This structure is disclosed for example in Japanese Laid-open Patent Application No. 6-82892. In a camera disclosed in Japanese Laid-open Patent Application No. 9-244116, the autofocus IC is placed underneath the release button and above the light projecting-receiving section. In this camera, the light projecting-receiving section is mounted in an upper portion of the camera, and a printed circuit board for a control circuit is placed above the light receiving side of the light projecting-receiving section, and the release button is provided on the top side of the control circuit board, whereas the autofocus IC is mounted on the bottom side of the control circuit board.
There is a camera wherein the autofocus IC and the release switch that are placed underneath the release button, and is not placed above the light projecting-receiving section. Since the release button is usually located on a top side of the camera body, where the autofocus IC is placed under the release button, a mounting space of a certain height must be provided in an upper portion of the camera, enough to mount the release button, the release switch, the autofocus IC, the flexible printed circuit board and so forth. In practice, a hard base plate is inserted in between the release switch and the autofocus IC, so that the pressure applied onto the release button may not be transmitted to the autofocus IC. The base plate still more increases the necessary height of the mounting space. Because of such a mounting space of a certain height, the height of the camera body cannot be reduced so much.
Also where the autofocus IC is placed above the light projecting-receiving section, it is difficult to reduce the height of the camera body. Where the release button, the release switch and the autofocus IC are placed above the light projecting-receiving section, reduction of the camera body height is still more difficult.
Moreover, where the autofocus IC is placed underneath the release switch, the autofocus IC is sometimes affected by noises that are generated from the release switch because of chattering or the like when the release switch is turned on or off, or by a ground line connected to the release switch. In that case, the subject distance signal from the autofocus IC becomes inaccurate.
In view of the foregoing, an object of the present invention is to provide an automatic focusing camera with an autofocus IC, which is improved in flexibility of dimensioning the camera body, especially in height of the camera body, and also makes the autofocus IC less affected by the noises.
According to the present invention, in an automatic focusing camera that automatically focuses a taking lens on a subject distance detected based on a detection signal from a light receiving element receiving light reflected from a photographic subject, an autofocus IC for calculating the subject distance from the detection signal is disposed at a position that is approximately equal in height to a release switch, and is shifted rearward of a camera body from the release switch. The release switch is disposed underneath a release button that is provided on a top wall of the camera body.
Since the autofocus IC is placed rearward from the release switch at about the same height as the release switch, there is no need for providing a mounting space for the autofocus IC under the release button. Therefore, the entire height of the camera body may be reduced by the mounting space for the autofocus IC. In addition, the autofocus IC is less affected by the noises generated from the release switch, because the distance of the autofocus IC from the release switch is increased as compared with the case where the autofocus IC is placed underneath the release switch. Furthermore, the noises from the ground line as well as from the release switch cannot easily overlap the detection signal from the light receiving element and the output signal from the autofocus IC as well.
According to a preferred embodiment, the autofocus IC and the release switch are mounted on a flexible printed circuit board that is made of a single sheet having a plurality of sections connected to each other through flexible strips. The autofocus IC, the release switch and the light receiving elements are mounted on different ones of the sections from each other, and are disposed in predetermined positions by bending the flexible strips. This embodiment facilitates mounting the respective elements for the automatic focusing.
By mounting the autofocus IC in an inclined posture to a horizontal plane of the camera body, it becomes possible to dispose the autofocus IC in an upper position of the camera body, without the need for increasing the thickness of the camera body. Especially where the top wall of the camera body slopes down to the rear wall, this configuration is desirable, because it makes possible to dispose the autofocus IC behind the release switch without the need for redesigning the camera body.